According to the prior art, wall switches are known for turning on and turning off luminaries such as lamps, overhead lighting, etc. Furthermore, it is known to include dimmer switches and rheostats for controlling the level of brightness of such luminaries when they are turned on.
More recently, circuits have been developed for detecting the presence of a person in a room and in response controlling ancillary systems such as lighting, security alarms, etc. For example, U.S. Pat. No. 5,015,994 (Hoberman et al) discloses a security light controlled by a motion detector. According to this system, a photoelectric device is provided such that the security light is illuminated in response to motion only when there is an insufficient amount of ambient light available from other sources.
U.S. Pat. No. 5,153,560 (Ichikawa) discloses an apparatus for detecting the presence of a person inside of a room having a door. The disclosed system incorporates an infrared sensor and a pressure pulse-wave sensor to determine when the door has been opened. Logic circuitry is provided for receiving signals from the infrared sensor and from the pressure pulse-wave sensor such that when the infrared sensor is triggered after the pressure pulse-wave sensor, the logic device produces a signal indicating entry of a person, whereas when the pressure pulse-wave sensor is triggered after the infrared sensor, the logic device produces a signal indicating the exit of a person from the room. In this manner, the signals may be processed by the logic circuitry to ascertain the presence or absence of a person.
Additional prior art is known directed to various motion detection techniques, such as U.S. Pat. No. 4,823,051 (Young), U.S. Pat. No. 4,447,726 (Mudge et al), U.S. Pat. No. 4,660,024 (McMaster), U.S. Pat. No. 4,952,911 (D'Ambrosia et al), U.S. Pat. No. 4,967,183 (D'Ambrosia et al), U.S. Pat. No. 5,019,802 (Brittain et al), U.S. Pat. No. 5,023,593 (Brox), U.S. Pat. No. 5,276,427 (Peterson), U.S. Pat. No. 4,772,875 (Maddox et al), U.S. Pat. No. 4,510,488 (St. Jean et al), U.S. Pat. No. 4,494,074 (D'Ambrosia et al), U.S. Pat. No. 4,928,085 (DuRand, III et al), U.S. Pat. No. 5,077,548 (Dipoala), U.S. Pat. No. 5,107,249 (Johnson), U.S. Pat. No. 5,281,961 (Elwell), U.S. Pat. No. 4,943,800 (Ikeda et al).
The above-discussed prior art systems disclose various applications of infrared radiation detection and pressure pulse-wave detection for intrusion systems, and environmental control systems. However, the existing prior art systems allow for only limited energy conservation and utilize relatively unsophisticated sensors. More particularly, in many existing systems a fixed threshold is set against which the infrared, pressure pulse-wave, etc., sensor signals are compared. However, the fixed threshold established in such prior art systems generally drifts over time, such that the prior art devices are vulnerable to microphonics and background noise in the case of pressure pulse-wave detection, as well as being vulnerable to rapid environmental changes (i.e. temperature, humidity, wind, ambient light, etc.).